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Landscape Change Detection with Quickbird and Ikonos Satellite
Images and Historic Aerial Photographs,
Arctic National Wildlife Refuge, Alaska
Janet C. Jorgenson, Megan Boldenow, Alan Brackney, & Cashell Villa
U.S. Fish and Wildlife Service, Fairbanks, Alaska
Northern Alaska is one of the fastest warming regions of the world, with increases documented in
both air and soil temperatures over the past three decades. Interpretation of historical
aerial photographs and satellite images is a practical means of documenting historical and future
landscape-scale changes.
Ecological regions of the Arctic NWR
The Arctic National Wildlife Refuge spans 310 km, from boreal forest across the Brooks Range to the Arctic coastline. In each of seven ecological regions
of the Refuge, we randomly selected five study sites from areas for which summer imagery was available for three time periods: 1947-1955, 1978-1985,
and 2000-2009. Historic photographs were scanned and georeferenced to current Quickbird and IKONOS satellite images. At each site, a grid of 100 points
was established. Using ARC-MAP, we visually interpreted each point for vegetation type, microtopography, and disturbance. We completed interpretation
of 3500 points in June 2011 and will now summarize data by ecological region, terrain type, and vegetation type.
Stratified-random sample of sites (red dots) in major ecoregions
(delineated in red), chosen from overlap area between
currently-archived Quickbird (purple) and Ikonos images (blue),
and aerial photographs from 1947-1950 and 1978-1985 (not shown).
1984
2003
Preliminary results show that over the past half century the southern forested portion of the Refuge changed more than the northern tundra part. Almost two thirds of the boreal forest region
changed over a 50 year period, mainly due to frequent forest fires. Drying of lakes was also common.
On the northern coastal plain, about one half of the points changed. The most common change there was ground subsidence and alteration of surface drainage patterns due to melting
of soil ice. The adjacent northern Brooks Range foothills and Beaufort Sea coast regions each had about one third of points change, due mainly to soil ice melting and coastal erosion
and deposition processes.
The three regions in the Brooks Range and Davidson Mountains had only about 10% changed, often due to river channel migration.
Northern coastal plain: Ice-wedge polygon topography. Increased
roughness of slope in center, due to melting of subsurface ice.
Changes in the southern part of the refuge were generally related to drying while those on the northern tundra more often involved wetting and were related to ice melt on land and sea.
1955
1950
1978
2000
2003
Boreal forest: Lake drying.
Beaufort Sea Coast: coastal erosion and accretion
1949
1955
1978
1978
2003
2000
Boreal forest: Area burned in 1950, leaving large unburned patch of spruce (black), and causing landslides in SW corner.
In 1986 most of the spruce patch burned but young deciduous-spruce forest on east side (red) did not.
Glacial river valley in northern Brooks Range: Channel changes on alluvial fan and increased channel incision
above fan. Increased shrubs in NW corner.